The invention concerns an electrically-instrumented technique of diagnosing the presence of a neoplast in a mucous membrane sample.
The response of a live sample of mucous membrane to alternating current is typically that of an R-C circuit whose resistive portion is determined by the properties of the intercellular liquid and whose capacitive portion corresponds to the diaphragm capacitance of all the cells in the sample, arranged in a series of layers between the electrodes which supply the alternating current to the sample. The diaphragm capacitance, especially, has extraordinary physiological importance. Other equivalent electrical components exist in such sample, but they can be neglected, particularly when the current flow through the sample is negligible.
It has been experimentally determined that changes in the electrical impedance of a membrane sample are indicative of morphologic changes in such sample, such as the presence of neoplasms. Accordingly, circuitry has been developed in the prior art for measuring the absolute value of the voltage across the test sample when such sample is supplied by current via an amplitude-modulated generator and one or more resistors. Unfortunately, since such impedance component is made up of resistive and capacitive portions (i.e., real and imaginary parts of the measured impedance), a relatively large change in one of the components of the measured voltage would have to take place before a statistically significant change in the total measured voltage across the test sample can be measured and evaluated, so that the resulting apparatus is relatively insensitive.